This invention relates generally to mixing valves with independent inlet ports that feed a common outlet and particularly to a fluid pressure actuated valve for mixing liquids in a DNA synthesizer and in other systems in which fluids are mixed.
Mixing valves with independent inlet ports feeding a common outlet are well-known. Prior mixing valves require either manual control or employ electrical or pneumatic actuators to control the positions of valve seals relative to corresponding valve seats to switch the valve between inlets. Manually controlled mixing valves are incompatible with the concept of modern automated systems. Prior electrically or pneumatically controlled mixing valves typically require secondary control circuits that must be either manually controlled or include secondary control system to insure proper operation. Such prior mixing valves are of necessity complicated and expensive, and they are often unreliable in providing the desired control of fluids to be mixed.
The electrically actuated mixing valves includes a compact solenoid operated mixing valve with a small dead volume. This device has the disadvantage of requiring an electrical signal for actuation, which creates the danger of fire or explosion when used to control the flow of highly flammable fluids. The control system for the solenoid is expensive and does not have the desired degree of reliability for use in analytical instrumentation.
A mixing control valve arrangement sometimes used in hydraulic drives of heavy machinery and equipment includes two ordinary check valves connected together with a T-shaped conduit. This arrangement is unsatisfactory for scientific analytical instrumentation because of the large dead volume in the conduit and the intermixing of the fluids in the two input legs.